There is a multi-RAT user equipment (UE) having capability in which the multi-RAT UE can access two or more radio access technologies (RATs). In order to access a specific RAT, connection to a specific RAT can be established on the basis of a UE request, and data transmission/reception can be achieved on the basis of the UE request. However, although the multi-RAT UE has the capability to access two or more RATs, the multi-RAT UE cannot simultaneously access multiple RATs. In other words, although a current UE has multi-RAT capability, the UE cannot simultaneously transmit and receive data through different RATs.
Since the related art multi-RAT technology does not required interworking between a wireless local area network (LAN) and a cellular network, there lies a problem in that the overall system efficiency is poor. Moreover, even if the user equipment (UE) is available for simultaneous access (or connection) to the Multiple RAT, by supporting only flow mobility/IP-flow mapping at the network level without any control in the wireless level, simultaneous connection (or access) to the Multiple RAT was made available.
However, such related art technology has its limitations in enhancing the overall network efficiency, since the network situation is not accurately understood, and since the RAT selected is focused mainly on the user equipment (UE). Most particularly, as the access of the user equipment to multiple communication systems has become available, although methods for allowing the user equipment to efficiently perform data shifting from one specific communication system to another communication system have become required, such research has not yet been carried out.